1. Field of the Invention
The present invention relates to a transparent conductive laminated body, which is transparent in visible light region, having a conductive thin film on a film substrate. The transparent conductive laminated body of the present invention is used in usages of transparent electrodes for new display methods applied liquid crystal displays, and electroluminescence displays and touch panels etc. besides and antistatic and electromagnetic wave interception, etc. for transparent goods
2. Description of the Prior Art
As a conventional transparent conductive thin film, a so-called conductive glass in which indium oxide thin film is formed on a glass plate is known well, but since a substrate is made of glass, the conductive glass is inferior in flexibility and workability, and it is not suitable for a certain usage. Therefore, in recent years, a transparent conductive thin film in which various kinds of plastic films including polyethylene terephthalate film is used as substrate are often used in the light of advantages, such as, a flexibility and workability etc. in addition to excellent shock resistance and lightweight.
However, transparent conductive thin films using the film substrate have a problem that transparency is decreased because of a large light reflection factor on surface thereof, and also have a problem that electric resistance is increased or disconnection of circuits may occur because of blemish given while in use since the conductive thin film is inferior in abrasion property. Especially in conductive thin films for touch panels, a pair of films facing countered to each other through a spacer are strongly contacted at depressed dots from the panel plate side of one of the pair, and therefore it is required for the films to have excellent durable characteristics resisting a strong depressing impact, that is, dotting property. However, since an excellent dotting property was not realized in the transparent conductive thin films using the above described film substrate, the films had a problem that only a short life as a touch panel could be realized.
In Japanese Patent Application Laid-Open (JP-A) No.6-222352 A, as a solution for the above described problem, a method of obtaining a transparent conductive laminated body is proposed in which a film with a specific film thickness is used as a film substrate, and onto one face of the film a thin film of dielectric substance with a light index of refraction smaller than a light index of refraction of the film substrate is formed, and further a transparent conductive thin film is sequentially formed thereon, and moreover onto the other face of the film substrate another transparent substrate is adhered through a transparent pressure sensitive adhesive layer. In this transparent conductive laminated body, while transparency and abrasion property of the conductive thin film are improved, dotting property as a material for touch panels is also improved.
There is also proposed a transparent conductive laminated body comprising a transparent film substrate, and a first transparent dielectric thin film, a second transparent dielectric thin film and a transparent conductive thin film that are formed on one side of the substrate in this order from the side of the substrate, wherein the laminate satisfies the relationship: the refractive index of the second transparent dielectric thin film<the refractive index of the film substrate≦the refractive index of the first transparent dielectric thin film<the refractive index of the transparent conductive thin film (see Japanese Patent Application Laid-Open (JP-A) No. 2002-326301). This transparent conductive laminated body can form a touch panel that shows improved dotting property when used in a bended form. According to Japanese Patent Application Laid-Open (JP-A) No. 2002-326301, however, a mixture of organic and inorganic materials is used for the first transparent dielectric thin film formed on the transparent film substrate, and thus it is not easy to adjust the optical properties such as transparency. There is also proposed a transparent conductive laminated body comprising a transparent film substrate, and a first transparent dielectric thin film, a second transparent dielectric thin film and a transparent conductive thin film that are formed on one side of the substrate in this order from the side of the substrate, wherein the laminate satisfies the relationship: the second transparent dielectric thin film<the transparent conductive thin film≦the first transparent dielectric thin film (see Japanese Patent Application Laid-Open (JP-A) No. 2000-301648). This transparent conductive laminated body is reported to be able to suppress coloration of transmitted light. Japanese Patent Application Laid-Open (JP-A) No. 2000-301648 discloses various methods for forming the first transparent dielectric thin film on the transparent film substrate, but none of the methods has a sufficient rate of film production.